Color photography



Patented Nov. 2, 1943 2,333,106 coLoR rnoroomirnr John David Kendall and Douglas James Fry, Ilford, England, assignors to Ilford Limited, Iliord, Essex, England, a British company 7 No Drawing. Application May 21, 1941, Serial No.

394,562. In Great Britain June 26, 1940 12 Claims.

This invention relates to the production of photographic dyestufl images and to dyestuff intermediates for the production of such images.

It is known that a colored photographic image may b formed simultaneously with the silver image obtained by developing an exposed photographic silver halide emulsion with an aromatic amino developing agent, e. g. an asymmetric dialkyl p-phenylene diamine, if a substance known as a color-former is present, for example in the developing solution or in the silver halide emulsion. The colored image may be revealed by bleaching out the silver image with Farmers reducer or other photographic bleaching agent.

It is an object of this invention to provide a new range of color-formers which yield blue-grey and neutral grey photographic images. It is a further object of the invention to provide a colordevelopment process employing such color formers. Another object of the invention is to produce. photographic images in neutral tones. Other objects of the invention will appear hereinafter.

According to the present invention, a process of color development is provided in which a reducible silver salt image is developed with an aromatic amino color-developing agent-in the presence ot a color-former which is a 4-hydroxypyrazole of the general formula:

propyl or higher alkyl group, an aryl group,.e. g.-

a phenyl or naphthyl groupor an aralkyl group e. g. a benzyl group or a naphthyl-methyl group. Altematively the group A may be .a carboxylic amide group or substituted carbox'ylic amide group of the formula to above, or heterocyclic groups. R: and Re may also together form the residue of a cyclic nucleus, e. g. a cyclohexane nucleus, a morpholine nucleus or a piperidine nucleus. The groups R1, R2 and R3 referred to above may themselves be substituted,'e. g. aryl groups may be substituted with alkyl, hydroxy, alkoxy, oxyalkyl, amino,- nitro sulphonic and carboxylic groups and halogen atoms.

The group B of the formula may be, for example, a benzene group or a naphthalene group and such groups may themselves be substituted with other groups, e. g. alkyl, hydroxy, alkoxy,

oxyalkyl, amino, nitro sulphonic and carboxylic groups and halogen atoms.

The color formers of this invention yield grey, blue-grey and blue images and they areof particular value in the production of photographic dyestuii images in neutral tones. It is found that the amides and substituted amides, are preferable from the point of view of obtaining a good neutral grey image. Increase in the size of the N-aryl group appears to have the effect of making the image tone more blue.

The color formers may conveniently be prepared by the following general method. First a 'y-halogen aceto-acetic ester is coupled with an aryl diazonium. compound andthe product is then treated with a basic substance whereupon ring closure takes place. If a weak inorganic base is employed the product obtained is a compound wherein the group A is a,carboxylic ester ing this latter product the elements of carbon dioxide are removed and the product obtained is a compound wherein the group A is a hydrogen atom. v

Compounds wherein A is .a carboxylic amide group or substituted carboxyli c amide group may be obtained by heating the corresponding comwhere itzand R3 are the same or diflerent and are hydrogen atoms, hydrocarbon groups, e. 8. any of the alkyl, aryl or aralkyl groups referred pounds where A is a carboxylic ester group with ammonia or primary or secondary amines. Ex-

amples are mono-., or di-alkylamines, e. g. ethyl amine, diethylamine and higher homologues,

monoand di-arylamines, e. g. aniline, diphenylamine and naphthylamines', monoand di-. aralkylamines, e.'- g. benzylamine, alkyl aryl-'- amines, e. g. N-ethylaniline, 'alkyl aralkyl amines,

e.. g. N-ethyl benaylamine, aralkyl arylamines, e. g. benzyl aniline, heterocyclic amines, e. g. piperidina'morpholine, cyclohexylamine and the amino derivatives of pyridine, quinoline, thia- I and dinaphthylamines.

zoles, oxazoles, pyrimidines, quinazolines, and the like, and diamines, e. g. oand p-phenylene-diamine, benzidine, dianisidine, diamino stilbenes Aryl nuclei present in the-amines may themselves be substituted, e. g. by alkyl, nitro, halogen, alkoxy or oxyalkyl groups. Where the amine employed is a diamine, reaction may take place at bothamino groups so that the final product contains two 4-hydroxy pyrazole nuclei.

The general reactions set out above may be illustrated as follows:

R10-0C-CHTCO-(7H2X couple with aryl diazonium compound R1O-0 C- (ill-C -CH2X ITIH dry] heat with alkali strong alkali weaker alkali Jr Jr 3 HO0C( fi-OH R1O0C-("J-.(|?-0H 1'7 cn N\ cn If N Aryl Lryl i heat 1 heat with amine no 0 on H NH N CH R2 R: N A 1 /N-0CfiC-OH V R: N\ /CH N Aryl The color formers or this invention may be incorporated in the .developing solution or in the photographic silver halide emulsion. In general they are very insoluble'in water and have little tendency to diffuse from one layer to another in multi-layer film or to diffuse into the processingsolutions. Moreover, many of the color formers of this invention yield dye images which are as in-.- tense in the presence of the 'sulphite commonly contained in photographic develop ng solutions as they are in the absence of such sulphite As examples of aromatic amino color developing agents which may be employed according to this j invention there may be mentioned p-phenylene diamine and substitution derivativesthereof in which at least one of the amino groups is unsubstituted, 'e. g. p-aminodimethylaniline, 'p-aminodiethylaniline and p -aminodibutylaniline. Other examples are p-methylaminoaniline, p-ethylaminc-aniline, c'hloro-p-phenylenediamine, .1,2,5- toluylenediamine, 2-amino-5-diethylamino-toluene, N-p-aminophenylpiperidine, N-methyl- -N- hydroxyethyIsp-phenylene-diamine, N -butyl-N- hydroxyethyl-p-phenylenediamine and 'fl-v-dlhydroxypropyl-prphenylenedia'mine. matic amino-developin agents may housed in the formof their salts, which may be of inorganic ororganic type. The salts are inigeneral more stable than the free bases. Examples of suitable salts are the hydrochlorides, sulphates and acetates.

Color developing agents which are amino phenols, e. g.-p-amino phenol or o-phenylene di- Thesearc-- amines or derivatives thereof, e. g. N.N-diethyl-ophenylene diamine may also be employed.

By way of example a suitable developing solution (referred to for convenience in the subsequent examples as Developing solution A) containing a color-former in accordance with the present invention may be made up as follows:

Asymmetric diethyl-p-phenylene diamine The sodium sulphite may be omitted if desired.

As indicated above, the color formers of this invention yield dyeimages of neutral grey and blue-grey and blue tones. The color formers yielding grey images are of especial value in the production of fine grain blaok and white photographic images, e. g. by the process of Specification No. 2,173,739. In that specification the production of a neutral tone dye image is effected by the use of two separate color formers yield ing difierently colored images which in combination yield an image of neutral tone. A similar result can be. obtained by the use of the single color former of the present invention.

The following examples illustrate the invention:

EXAMPLE I (a) Preparation. of a-phenylhydrazo-p-keto-rychlor-butyric acid ethyl ester A solution of 3.72 grams of aniline in a mixture of 12 cos. of concentrated hydrochloric acid and 25 cos. of water was cooled in ice and there was'then added slowly a solution of 2.72 grams of sodium nitrite in 9 cos. of water. 'The mixture was stirred for ten minutes and was then added,

with stirring, to a cooled solution of 6.6 grams of 'y-chlor acetoacetic acid ethyl ester in 35 cos. of ethyl alcohol. Successive amounts of crystalline sodium acetate amounting in all to .125 grams were then added. The product separated as a yellow solid and was removed by filtration, washed with aqueous ethyl alcohol and recrystallised from ethyl alcohol. M. P. 93 C.

(N. B.-The corresponding 'y-brom compound can beprepared by using an equivalent. quantity of 'y-brom aceto acetic acid ethyl ester. It melts at C. and can be used inequivalent quantity instead of the 'y-chlor compound in the further reactions described below.)

clroxide in 8 cos. of water at a temperature of 50-60 C. The mixture was then boiled for five minutes, cooled, extracted twice with ether to remove oily impurities and then added to asolutionpf 3 grams of concentrated hydrochloric acid in 3 cos. of water. The product precipitated as "an oil which hardenec on stirring. The product was recrystallised iron. hloroform solution and had a melting point of 154 C. This product when included in Developing solution A and used for the development of an exposed silver chloride emulsion yielded a neutral grey image in addition to the silver image.

EXAMPLE 11 Preparation of 1-phenyl-4-hydrox'ypyrazole 2.55 grams of 1-phenyl-4-hydroxy-pyrazole-3- carboxylic acid preparedas in Example I (b) was heated on an oil bath for one hour at 220-250 C. The mass was then cooled and repeatedly extracted with hot water. The combined hot water extracts deposited an oil which crystallised out on cooling. The crystalline product was removed by filtration, washed and recrystallised from hot water. It had a melting point of 120 C.

This product when included in Developing solution A and used for the development of an exposed silver chloride emulsion yielded a bluish grey image in addition to the silver image.

EXAMPLE III Preparation of 1 -phen1 l 3-oarbethozy- 4-hydroxy pyrazole 11.5 grams of e-phenylhydrazo-B-keto-'y-chlor butyric' ethyl ester prepared as in Example I (a) was added in portions to a hot solution 'of 7.5 grams of potassium acetate in 50 cos. of ethyl alcohol. The mixture was boiled for fifteen minutes, cooled, and diluted with 200 cos. of water. The product separated on standing and was removed by filtration and washed with water. It had a melting point of 85 C.

This product when included in Developing solution A and used for the development of an exposed silver chloride emulsion yielded a neutral grey image in addition to the silver image.

EXAMPLE IV Preparation of 1-phenyl-khydrozy-pyraaole- 3-carboxylic acid anilide 1.16 grams of 1-phenyl-3- :arbethoxy-'i=-hydroxy-pyrazole prepared as in Example III and 0.6 gram of aniline were heated in an oil bath for two hours at 200 C. The product was cooled, washed with ethyl alcohol and filtered. The product melted at 225 C. This product when included inDeveloping' solution A and used for the development of an exposed silver halide emulsion yielded an excellent neutral grey image in addition to the silver image. 7

The following are additional examples of color formers according tothis invention which may be made by methods analogous to those set forth above:

p. p'-Di-(1-phenyl-4-hydroxy-pyrazole-3 car-' bonylaminot-diphenyl, M. P. 264 C. with decomposition, yielded a grey image of slightly blue tone.

p. p'-Di-(l-phenyl-i-hydroxy-pyrazole 3 carbonylamino) -diph.enyl methane, M. P. 199 C. yielded a grey image of slightly blue tone.

1-phenyl-4-hydroxy-pyrazole-3-carboxylic acid p-chloranilide, M. P. 246 C. yielded an excel lent neutral grey image.

1-phenyl-4-hydroxy-pyrazole-3-carboxylic acidm-xylidide, M. P. 199 0. yielded a grey image of slightly blue tone.

1-p-naphthy1-4-hydroxy-pyrazole, M. P. 158 C.

yielded a deep blue-grey image.

l-p naphthyl-ii-carbethoxyi-hydroxy pyrazole, M. P. 107 C. yielded a grey image of slightly blue tone.

1-p-naphthyl-4-hydroxypyrazole 3 carboxylic acid anilide, M. P. 266 C. with decomposition,

yielded a blue grey image.

p. p-Di-(1-p-naphthyl-4-hydroxy' pyrazole 3 carbonylamine) diphenyl, M. P. 270 C.- yielded a grey image. 1-p-naphthyl-4-hydroxy-pyrazole-3 carboxylic acid-p-chloranilide, M. P. 288 C. yielded a grey image of slightly bluish tone.

lo l-p-naphthyl-4-hydroxy-P razole-3 carboxylic acid-m-xylidide, M. P. 193 C. yielded a grey image of very slightly bluish tone.

1-p-tolyl-4-hydroxy-pyrazole, M. P. 123-126 C.

yielded a blue-grey image.

1-p-tolyl-3-carbethoxy-4-hydroxy Q pyrazole, M.

1 :4-Di-(1-p-chlorpheny1-4-hydroxy-3-carbonylamino)-benzene, M. P. 260 0., yielded a grey image of slightly bluish tone. l-p-chlorphenyl-i-hydroxy pyrazole,.M. P. 123

C. yielded a bluish grey image. l-p-chlorphenyl-3-carboxy-4-hydroxy pyrazole, M. P. 273 C. yielded a grey image of slightly bluish tone.

As a modification, the production of colored images by means of the color-formers of this invention may be applied tocolloid layers sensitised by bi-chromate. Thus the color-formers 1-p-naphthyl-4-hydroxy-pyrazole-3 carboxylic acid,.M. P. 188 0. with decompositionJielded a blue image. I

may be incorporated in bichromate-sensitised colloid layers (e. g. gelatin, gum arable or albumin) the layers exposed, the unexposed colloid removed, for example by treatment with hot water, and the color developed in the exposed portions by treatment with p-nitroso-dialkyl-aniline or its derivatives.

The color formers according tothis invention 'are not restricted in their use to the processes of color development referred to above. Thus they may be treated with;diazo compounds to form azo dyes which may then be differentially bleached to form dyed images, e. g. by the proces of Christensen, British Patent Specification No. 133,034. Thus, for example, the color-formers of this invention when coupled with benzene diazonium chloride yield yellow to orange dye images.

., Whatweclaimis: 1.- Process for the production'ofphotographic dyestufl. images which comprises developing a reducible silver salt image with an aromaticamino color-developing agent in the presence of a color.- Iormer which is a compound of the, general formula:

' A--i c-on where A is selected from the at... consisting of boxylic ester groups, carboxylic amide groups, and substituted carboxylic amide groups, and B is selected from the class consisting of aryl groups and substituted aryl groups,

2. Process for the production of photographic images which comprises developing an exposed silver halide emulsion with an aromatic amino color-developing agent in the presence of a colorformer which is a compound of the general formula: Y

where A is selected from the class consisting of the hydrogen atom, the carboxyl group, carboxylic 'ester groups, carboxylic amide groups and subwhere A is selected from the class consisting of the hydrogen atom, the carboxyl group, carboxylic ester groups, carboxylic amide groups and substituted carboxylic amide groups, and B is selected from the class consisting of aryl groups and substituted aryl groups.

dyestuff images which comprises developing an exposed silver halide emulsion with an asymmetric diallgyl-p-phenylene diaminedeveloper in the presence of a color-former which is a compound of the general formula:

AC-C-OH II I! I N\ /CH where A is selected from the class consisting of the hydrogen atom, the carboxylic group, carboxylic ester groups, carboxylic amide groups and substituted carboxylic amide groups, and B is s'elected from the class consisting of aryl groups and substituted aryl groups.

5. A photographic element bearing a light-sensitive silver halide emulsion containing acolorformer which is a compound of the general formula: 1

' A-o-'-o-oH where A is selected from the class consisting of the hydrogen atom, the carboxyl group, carboxylic estergroups, carboxylic amide groups and substituted carboxylic amide groups, and B is selected from the class-consisting of aryl groups and substituted aryl groups.

6. A multilayer photographic element in which at least one of the layers consists of a light-sensitive silver halide emulsion 'containinga colorvformer which is a compound of the general for- II N CH where A is selected from the class consisting of thehydrogen atom, the carboxyl group, carboxylic ester groups, carboxylic amide groups and sub:

stituted carboxylic amide groups, and B is se- 4. Process for the production of photographic 1 lected from the class consisting of aryl groups and substituted aryl groups.

7. A process for the production of photographic dyestufi images which comprises developing a photographic element containing a reducible silver salt image with a primary aromatic amino colordeveloping' agent in the presence of 1-phenyl-4- hydroxy-pyrazole-3-carboxylic acid.

8. A photographic element bearing a light sensitive silver halide emulsion containing l-phenyl- .4-hydroxy-pyrazole-3-carboxylic acid.

9. A process for the production of photographic dyestuff images which comprises developing a photographic element containing a reducible silver salt image with a primary aromatic amino colordeveloping agent in the presence of l-phenyllhydroxy-pyrazole-3-carboxylic acide anilide.

-10. A photographic element bearing a light sensitive halide emulsion containing 1-phenyl-4-hydroxy-pyrazole-3-carboxylic acid anilide.

11. A process for the production of photographic .dyestufi images which comprises developing a photographic element containing a reducible silver salt image with a primary aromatic amino color-developing agent in the presence of 1- phenyl-4-hydroxy-pyrazole'-3-carboxylic acid-pchloramlide.

12. A photographic element bearing alight se sitive. silver halide emulsion containing l-phen lanilide.

4-hydroxy-pyrazole-3-carboxy1ic acid-p-chlor- JOHN DAVID KENDALL. DOUGLAS JAMES FRY. 

